Formation with certain alcohols of acrylamide groups on polyacrylonitrile in zinc chloride solution



Sept. 13, 1960 A. ARMEN ErAL 2,952,651

FORMATION WITH CERTAIN ALcoHoLs oF ACRYLAMIDE GROUPS ON POLYACRYLONITRILE IN ZINC CHLORIDE SOLUTION Filed May 7, 1958 8o c o z5 y /Of 20 -O/ O Mo/e Per Cen/ of Q/y/ cry/om/oe Un ifs in Hcry /on//r//e FaQ/ner Produc/l Rene/fon 77h06, Hou/35 IN V EN TORS. ra/y rmel? nited States Patent l FORMATION WITH CERTAIN ALCOHOLS OF ACRYLAMIDE GROUPS ON POLYACRYLO- NITRILE IN ZINC CHLORIDE SOLUTION Ardy Armen and Stanley A. Murdock, Concord, Calif., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Filed May 7, 1958, Ser. No. 733,624

10 Claims. (Cl. 260-29.6)

The chief aim and major concern of the present invention is to provide an improved process for modifying polyacrylonitrile of the fiber-forming variety so as to enhance its dye-receptivity while the polymer is dissolved in an aqueous, zinc chloride-containing solvent therefor as a spinnable composition that is adapted to be wetspun (by salt-spinning procedures according to the conventional technique) into readily dyeable lamentary and the like shaped articles and products.

Y To this end, dye-receptive alkyl acrylamide groups or units may be introduced into fiber-forming polyacrylonitrile while it is in the form of a wet spinnable, liberforming solution in an aqueous, polyacrylonitrile-dissolving solvent comprised of zinc chloride by a method Ywhich, surprisingly and simply enough, comprisesradrd- `ing to the polymer-containing aqueous saline spinning solution a minor proportion of tertiary alcohol or a benzyl alcohol, or a mixture thereof, as hereinafter delined, and heating the mixture at a temperature between about 50 C., preferably at least about 60 C. and 80 C. or so for a period of time between about 0.1 and 25' hours until between about 2 and 25 mole percent of the nitrile groups preferably between about 8 and 20 mole percent thereof, are converted to alkyl acrylamide units corresponding to the substituents introduced by the particular alcoholic reactant (or mixture of reactants) employed. The resulting acrylonitrile polymer composition is especially well adapted to be salt-spun into excellent quality acryonitrile polymer synthetic textile fiber products, using the Well known wet spinning process in which aquagel intermediates are formed. The resulting fiber products which are obtained after irreversible drying of the aquagel intermediate that is coagulated from the modified spinning composition have excellent receptivity of and unusual affinity for dyestuffs of the acid class.

The tertiary and benzyl alcohols which may be utilized in the practice of the present invention to modify the liber-forming polyacrylonitrile while it is dissolved in the zinc chloride-containing aqueous saline solvent therefor are any of those of the respective formulae:

)ramon wherein each X is independently selected from the group consisting of halogens of atomic number 17 to 35 (i.e., chlorine and bromine), and alkyl radicals containing from l to about 4 carbon atoms; and n has a whole number value from to 5. Advantageously, the dis- ICS solved polyacrylonitrile is modied with tertiary-amyl alcohol (C2H5(CH3)2COH), tertiary-butyl alcohol (CHSMCOH) benzyl alcohol, or mixtures thereof. Excellent results may also be obtained, however, by use of such alcohols as 3-methyl-pentane-3-ol ((C2H5)2CH3COH), Z-methylpentane 2 ol (C3H7(CH3)2COH) 3-ethyl-pentane-3-ol (C21-l5) 3COH) 3-methyl-hexane-3-ol in the polymer molecule, as typified by the following:

I (IDN toNHG f f i CH CH- -CH Oli- L\ V /y T- /z I wherein the value of z is from 2 to 25 mole percent, preferably from 8 to 20 mole percent, of the sum of y plus z, and the G substituent, depends upon the particular alcohol (or alcoholic mixture) used for the modification of the polyacrylonitrile.

This modification occurs by the following reactions: with tertiary alcohols of Formula I The precise quantity of the alcohol that is utilized depends upon the degree of modification of the polyacrylonitrile that is desired (i.e., the proportion of recurring alkyl acrylamide units desired to be introduced therein), the extent towards completion which the reaction is permitted to proceed, and the particular alcohol utilized. In any event, the quantity to employ in any given situation can be readily calculated, taking the above factors into account. In many cases, without intending to be limited thereto, satisfactory results can be achieved when between about 2 and 25 mole percent, advantageously about 10 mole percent, of the alcohol is employed, based on the molar quantity of polyacrylonitrile being modified in the spinning solution.

The aqueous salt solution comprising zinc chloride which is employed as the solvent for the polyacrylonitrile in the practice of the invention is preferably a 55 to 65 percent by Weight solution, preferably about a 60 weight percent solution, of zinc chloride as the sole saline constituent.

The amount of polyacrylonitrile that is modified in `the aqueous saline spinning solution may advantageously be between about 2 and 20 percent by weight, based on the weight of the polymer-containing spinning solution. More often, it may be more beneficial for .the spinning solution to contain between about 6 and 15 weight percent, and even more beneficially from 8.5 to 11.5 weight percent, of dissolved polymer. Generally, it is preferable for the polyacrylonitrile .that is modified to be in the desirable molecular weight range from about 20,000 to 60,000 (viscosimetrically determined as described in United States Letters Paten-t No. 2,763,636, at column 2, lines 37-41) and lthe solution itself in the viscosity range, measured at about 35 C., of from about 300 to 3,000 poises. Of course, lower and higher molecular weight polyacrylonitrile can also be modified to enhance its dyereceptivity by practice of the invention. The modified spinning solutions of the present invention can be saltspun in the known manner to form synthetic textile fiber products, or films if desired, using non-polyacrylonitriledissolving aqueous solutions of zinc chloride as the coagulating spin bath for the extruded products. Thus, the aqueous coagulating baths in which the aquagel structures are formed may -advantageously contain between about 25 and 50 weight percent of dissolved salt, more advantageously from about 30 to 45 weight percent, and preferably in .the neighborhood of 42-43 weight percent.

In conducting the alcohol modification of the dissolved polyacrylouitrile :to introduce alkyl acrylamide units therein, care should be taken to avoid use of too a temperature for too long a period of time in order to circumvent the possibility of hydrolyzing the acrylonitrile polymer in solution. Thus, when temperatures of about 95 C. are employed, it is generally found that appreciable hydrolysis results. This, of course, causes highly undesirable consequences in the procedure.

By way of further illustration, a series of polyacrylonitrile spinning solution samples were prepared containing about 10 weight percent of dissolved polyacrylonitrile having an average molecular weight of about .28,000 in 60 percent by weight aqueous zinc chloride solution. The polymer was prepared by direct solution polymerization of monomeric acylonitrile in the aqueous saline solvent. Prior to polymerization, the aqueous zinc chloride solution had been adjusted to pH 3 (measured at 10:1 by

volume aqueous dilution) with hydrochloric acid. I-nto each of the samples was added about 10 weight percent of tertiary-butyl alcohol, based on the weight of the dissolved polymer in the spinning solution. The alcoholic reactant was added to each sample as an equal weight mixture with 60 percent aqueous zinc chloride to prevent coagulation of .the polymer solution. Addition of the alcohol was made to each sample after it had been heated to the desired temperature of reaction at which it was maintained during the experimentation. Reaction temperatures of 40 C., 60 C., 80 C., and 95 C. were used. All of .the samples were stirred throughout their modification. In order to check hydrolysis, a non-alcoholic blank was run at 40 C. At reaction temperatures up .to about 80 C., the degree of hydrolysis incurred by .the modification was relatively insignificant. Hydrolysis became appreciable and occurred to an undesirable extent at 95 C. The results are set forth in the sole figure of the accompanying drawing, wherein the essential data from the several samples at various reaction temperatures are graphically portrayed by plotting reaction time against relative amide formation in the modified polyacrylonitrile, expressed as mole percent of alkyl acrylamide units found in the resulting polymer samples by means of infrared analysis.

By way of still further illustration, a modified spinning solution was prepared in the foregoing manner to obtain an acrylonitrile polymer in 60 percent aqeuous zinc chloride spinning solution containing about 10 percent by weight of dissolved polymer sol-ids consisting of polyacrylonitrile modified with tertiary-butyl alcohol 'for .10 hours at 60 C. until about 14 mole percent of alkyl acrylamide uni-ts were introduced in .the fiber-forming polymer. The spinning solution was extruded into an aqueous coagulating bath therefor containing about 43 weight percent of dissolved zinc chloride. A 750 hole spinnerette was employed in which each orifice had an individual `diameter of about 6 mils. After extrusion, the aquagel fibers were wet-stretched about twelve times for orientation, washed thoroughly with water, then irreversibly dr-ied 4for 30 minutes at 150 C. to synthetic acrylonitrile polymer fibers of about 3 denier/filament. The fiber product had excellent physical characteristics, being about commensurate in its essential textile proper- -ties to ord-inary polyacrylonitrile fibers. In addition, the modified fibers were found to be readily dyeable to level shades of coloration with Calcocid Alizarine Violet, an acid dye (Colour Index 1080); and many other acid dyestuffs of practical and commercial interest.

Excellent results similar to those demonstrated in the foregoing can also .be obtained when the acrylonitrile `is modified with tertiary-amyl alcohol, benzyl alcohol, or any other of the alcoholic reagents or their mixtures read upon by the Formulae I and I-I. Excellent results are also obtained when other degrees of modification of the' polyacrylonitrile in addition to those specifically illus- .trated are effected by the modifying treatment of thepresent process.

What is claimed is:

1. Method for improving the dye-receptivity of berj forming polyaoryloni-t-le while it is dissolved as a spin# nable solution in'an Vamount'between about 2 and 20` weight percent, based on the weight of said solution, in; an aqueous, polyacrylonitrile-dissolving, saline solution that is comprised of at least about 55 weight percent' based on the weight of the Aaqueous solution, of zinci chloride as the essential saline constituent, which methodt comprises adding to said solution of polyacrylonitrile at, least one alcohol selected from the sisting of the formulae:

Racon (1) in which each R is an independent alkyl radical con-vy taining from 1 to about 4 carbon atoms With the limita-i` tion that the total number of carbon atoms in all of the' R substituents of said alcohol of the Formula I is from` 3 to 7; and

group of those oon- @onion (Il)y in which each X is independently selected from they group consi-sting of halogens of atomic number 17 toi 35 and alkyl radicals containing from 1 to about 4 car-Q' bon atoms, and n has a whole number value from Oto 5; and mixtures of alcohols of the Formulae I and II, saidVv alcohol being added to said polyacrylonitrile solution in an amount that is suflicient, upon subsequent reaction, to convert -between about 2 and 25 mole percent of the nitrile groups in said polyacrylonitrile to alkyl acrylamide units; then heating the mixture of said alcohol and said solution of polyacrylonitrile at a temperature between -about 40 C. and about 80 C. for -a period of time between about 0.1 and 25 hou-rs until between about 2 and 25 mole percent of the nitrile groups of said polyacrylonitrile are converted to dye-receptive alkyl acrylamide groups corresponding to the alcoholic reagent utilized for the modification.

2. The method of claim 1, wherein the amount of alcohol employed is an -amount that is suflicient to convert between about 8 and 20 mole percent of said nitrile groups in said polyacrylonit-rile to said -alkyl acrylamide units.

3. The method of claim 1, wherein between about 2' and 25 mole percent, based on the molar quantity of polyaery-lonitrile vin solution, of said alcohol is added to `said solution of said polyacrylonitrile.

4. The method of claim 1, wherein said spinnable composition of polyacrylonitrile contains between about 6 and 15 Weight percent, based on the weight of the solution, of polyacrylonitrile dissolved in said aqueous, polyacrylom'trile-dissolving, saline solution and wherein about l0 mole percent, based on the molar quantity of polyaorylonitrile in solution, of said alcohol is added to said solution of polyacrylonitle 5. rIfhe method of claim 1, wherein said aqueous, polyacrylonitrile-dissolving, saline solution consists of between -about 55 and 65 Weight .percent of zinc chloride in Water, based on the weight of the aqueous solution.

6. The method of claim l, wherein said mixture of alcohol land `said solution of polyaorylonitrile is heated at a temperature between about 60 C. and about 80 C. 20 2,847,389

7. The method of claim 1, wherein said alcohol is tertiary-butyl alcohol.

8. The method of claim 1, wherein said alcohol is ter tiary-amyl alcohol.

9. The method of claim 1, wherein said alcohol is benzyl alcohol.

10. The method of claim 1 and including, in addition thereto and in combination therewith, the step of extruding said resulting spinnable solution of Ithe modified polyacrylo-nitrile after termination of said reaction with alcohol into an aqueous coagulating bath therefor to yform coagulated `shaped articles of said modified polyaorylonitrile in said bath.

References Cited in the file of this patent UNITED STATES PATENTS 2,648,647 Stanton et al Aug. 11, 1953 '2,719,144 Shearer et al. Sep-t. 27, 1955 Evans Aug. 12, 1958 

1. METHOD FOR IMPROVIDING THE DYE-RECEPTIVITY OF FIBERFORMING POLYARYLONITRILE WHILE IT IS DISSOLVED AS A SPINNABLE SOLUTION IN AN AMOUNT BETWEEN ABOUT 2 AND 20 WEIGHT PERCENT, BASED ON THE WEIGHT OF SAID SOLUTION, IN AN AQUEOUS, POLYACRYLONITRILE-DISSOLVING, SALINE SOLUTION THAT IS COMPRISED OF AT LEAST ABOUT 55 WEIGHT PERCENT, BASED ON THE WEIGHT OF THE AQUEOUS SOLUTION, OF ZINC CHLORIDE AS THE ESSENTIAL SALINE CONSTITUENT, WHICH METHOD COMPRISES ADDING TO SAID SOLUTION OF POLYACRYLONITRILE AT LEAST ONE ALCOHOL SELECTED FROM THE GROUP OF THOSE CONSISTING OF THE FORMULAE: 